TCLP Test Research Articles

Recycling application of heating pad waste as catalyst and adsorbent for organic and inorganic arsenic removal: Performance and mechanism

Heating pad waste (HPW), a magnetically recyclable material collected from disposable heating pads, is produced in amounts of millions of tons every year globally. HPW is mainly composed of Fe, C and O, directly disposal caused a waste of resource. In this paper, HPW was used to activate peroxymonosulfate (PMS) for roxarsone (ROX) degradation and as a functional adsorbent for the simultaneous adsorption of the released inorganic arsenic. After 2 h, 20 μM (1.5 mg-As/L) ROX was completely degraded, and the released inorganic arsenic was effectively adsorbed by HPW. Mechanism study proved •OH, SO4•−, and 1O2 were all existed in the HPW/PMS system, and •OH was the dominant reactive species. And the possible degradation pathways of ROX were further proposed based on the identified intermediates. Furthermore, the result of TCLP test showed that the leaching As concentration of the used HPW (0.146 mg/L) is far below the current identification standards for hazardous wastes-identification for extraction toxicity value on As (GB 5085.3-2007, 5 mg/L). This study adopted the strategy of “treat waste by waste”, achieved the resource utilization of HPW, brought economic and environmental benefit to environment remediation.

Facile fabrication of Fe/Zr binary MOFs for arsenic removal in water: High capacity, fast kinetics and good reusability

A water-stable bimetallic Fe/Zr metal-organic framework [UiO-66(Fe/Zr)] for exceptional decontamination of arsenic in water was fabricated through a facile one-step strategy. The batch adsorption experiments revealed the excellent performances with ultrafast adsorption kinetics due to the synergistic effects of two functional centers and large surface area (498.33 m2/g). The absorption capacity of UiO-66(Fe/Zr) for arsenate [As(V)] and arsenite [As(III)] reached as high as 204.1 mg/g and 101.7 mg/g, respectively. Langmuir model was suitable to describe the adsorption behaviors of arsenic on UiO-66(Fe/Zr). The fast kinetics (adsorption equilibrium in 30 min, 10 mg/L As) and pseudo-second-order model implied the strong chemisorption between arsenic ions and UiO-66(Fe/Zr), which was further confirmed by DFT theoretical calculations. The results of FT-IR, XPS analysis and TCLP test demonstrated that arsenic was immobilized on the surface of UiO-66(Fe/Zr) through Fe/Zr-O-As bonds, and the leaching rates of the adsorbed As(III) and As(V) from the spent adsorbent were only 5.6% and 1.4%, respectively. UiO-66(Fe/Zr) can be regenerated for five cycles without obvious removal efficiency decrease. The original arsenic (1.0 mg/L) in lake and tap water was effectively removed in 2.0 hr [99.0% of As(III) and 99.8% of As(V)]. The bimetallic UiO-66(Fe/Zr) has great potentials in water deep purification of arsenic with fast kinetics and high capacity.

Removal of arsenic in acidic wastewater using Lead-Zinc smelting slag: From waste solid to As-stabilized mineral.

High-arsenic wastewater has long been considered a major threat to ecological balance and human health because of its strong toxicity and high mobility. Herein, an environmentally friendly process was proposed for As removal and fixation in the form of As-stabilized mineral, using Lead-Zinc smelting (LZS) slag as the in situ Fe donor, neutralizer, and crystal seed. The slag was dissolved in the wastewater and released Fe and Ca ions, while simultaneously increasing the pH value of the solution to help scorodite synthesis. The dissolved Ca2+ ion preferentially reacted with SO42- ion in the form of CaSO4·2H2O precipitate as in situ "seeds" for As precipitation. The dissolved Fe(II) and As(III) ions were oxidized to Fe(III) and As(V) ions by H2O2, and later reacted with each other to generated amorphous ferric arsenate on the surface of CaSO4·2H2O, and then evolved into scorodite crystals with high stability. With a Fe/As molar ratio of 2, a reaction temperature of 90°C, and a reaction time of 12h, 98.42% of As was effectively precipitated from the wastewater with an initial As concentration of 7530.00mg/L. Moreover, the leached As concentration of the As-bearing precipitate in the TCLP test was 3.46mg/L. The concentration of the residual As and heavy metals ions in the final filtrate was lower than local wastewater discharge standards, successfully realizing the treatment of smelting wastewater. In summary, a prospective process successfully shows a great potential for co-treatment of LZS wastewater and slag, which could advance the large-scale disposal of LZS plants.

Stabilization of Waste-to-Energy (WTE) fly ash for disposal in landfills or use as cement substitute

This study investigated two approaches for managing Waste-to-Energy (WTE) fly ash (FA): (i) phosphoric acid stabilization of FA and disposal in non-hazardous landfills, so that it can pass the U.S. TCLP procedure and meet the U.S. Resource Conservation and Recovery Act (RCRA) standards; (ii) use of FA or phosphoric acid stabilized fly ash (PFA) as cement substitute in construction for avoiding disposal in landfills and reducing the consumption of Portland cement. The effect of stabilization was identified by TCLP tests and XRD quantification (QXRD), which showed that the economically optimal concentration for PFA to pass the RCRA was 1 mol/L H3PO4 (equivalent to 0.4 mol of H3PO4/kg of FA). Zn/Pb-phosphates were formed in treated ash by using high concentration H3PO4 (e.g., 3 mol/L). Thus, the hazardous FA was chemically stabilized to PFA, that were both discussed as cement substitute. QXRD and SEM results showed that both FA and PFA (1 mol/L H3PO4) chemically reacted with cement and water. Up to 25 vol% of the cement can be replaced by FA or PFA, with similar mechanical performance of cement mortars than that of reference. Testing by LEAF Method 1313-pH dependence showed that the FA and PFA cement mortars exhibited the same leachability of heavy metals; therefore, this study demonstrated the technical feasibility of utilizing either raw FA or stabilized PFA as supplementary cementitious material. The leachability of heavy metals in optimal FA or PFA 25 vol% cement mortar was under the U.K. WAC non-hazardous limits.

The Study on the Properties and TCLP of GGBFS-Based Heavy-Metal-Contaminated Soil Geopolymer

The objective of this study is to use the geopolymer technique to solidify/stabilize heavy metal contaminated soil. There are over 739,700 square meters of heavy-metal-contaminated sites in Taiwan; most sites are soil farmlands. These heavy metal contaminants in soil can also infiltrate into groundwater and cause more serious pollution problems. This study explores the possibility of using the geopolymer technique to solidify heavy metal contaminated soil (CS), stabilize heavy metal, and produce good mechanical and physical properties. The ground granulated blast furnace slag (GGBFS) was activated by an alkali solution to form a geopolymer binder that can be used to solidify CS and stabilize the heavy metal. The effect of GGBFS and CS mixing ratio on the mechanical and physical properties and the TCLP test was investigated. The test results show that the compressive strength of specimens made with a 1.5 CS/GGBFS ratio can reach 46.61 MPa and 47.66 MPa after curing for 14 and 28 days, respectively. TCLP tests show only 2 ppm Cu was detected from a geopolymer-treated contaminated soil sample. The influence of alkali solution, such as the molarity of the NaOH, SiO2/Na2O, and SiO2/Al2O3 molar ratio, were also evaluated. The specimens prepared with 8 M NaOH, 0.96 SiO2/Na2O, and 1.28 SiO2/Al2O3 molar ratio alkali solution have a compressive strength of 51.74 MPa and 58.63 MPa after 14 and 28 days of curing. The TCLP tests show no heavy metal ions leached from the sample.

Simple Compressive Strength Results of Sodium-Hydroxide- and Sodium-Silicate-Activated Copper Flotation Tailing Geopolymers

Geopolymers are created by mixing a source of aluminosilicates, which can be natural or by-products of other industries, with an alkaline solution, which dissolves the aluminates and silicates present in this source, where after a polymerization process, an N-A-S-H gel is formed, which is responsible for providing the properties that characterize geopolymers. Among the variety of existing geopolymers, those based on by-products from other industries stand out since they were demonstrated to be a less-polluting alternative for concrete production than ordinary Portland cement (OPC). Due to the above, it is essential to study copper flotation tailings as raw material to generate geopolymers. The excessive amounts of existing tailing deposits also produce different risks for the nearby communities. Therefore, using this industrial waste as a construction material would provide several environmental and economic benefits. This article reports on the experimental work carried out in the laboratory of the Sustainable Mining Research Center CIMS of the Engineering Consulting Company JRI, where the effect of the alkaline activator type on the compressive strength of geopolymers based on copper flotation tailings was analyzed. For this purpose, two geopolymeric mixtures were made with different kinds of alkaline activators; one activated using 100% NaOH and the other activated with 100% sodium silicate (SS). From the results, it was found that the geopolymers activated with 100% SS obtained the highest compressive strength, reaching 36.46 MPa with 7 days of curing at 90 °C, followed by the geopolymers activated with 100% NaOH, where a compressive strength of 22.98 MPa was obtained under the same curing conditions. On the other hand, it was found that both geopolymers created were not leachable according to the TCLP test performed, and thus, these geopolymers were classified as non-toxic materials. In addition, it was found that both geopolymers presented a high infiltration value, making them practically impermeable.

Novel GO/Fe-Mn hybrid for the adsorptive removal of Pb(II) ions from aqueous solution and the spent adsorbent disposability in cement mix: compressive properties and leachability study for circular economy benefits.

GO/Fe-Mn hybrids were prepared by a single-pot chemical precipitation method and were characterized using FTIR, XRD, Raman, zeta potential, and FESEM, which confirmed the impregnation of Fe/Mn onto GO sheets. The synthesized hybrids were successively applied in removing the Pb(II) ions from aqueous solution and later utilizing the spent adsorbent to increase the properties of cement. The adsorption capability of the synthesized hybrid was seen in a set of batch studies to find out that about 15min of contact time was required to remove 99% of the contaminant at a pH of 5 ± 0.2 and a dose of 0.83g/L. The mechanism of the adsorption process for the synthesized hybrid was well described by Elovich kinetic model with an R2 of 0.99 and Langmuir isotherm model, also with an R2 of 0.99. The desorption studies conducted using 0.1M HCl solution showed significant stability of the hybrid with a drop of 12% in the removal efficiency of Pb after up to five adsorption-desorption cycles. This points to an efficient adsorbent having potential for economical use. Later, the spent adsorbent was mixed with cement at ratios of 0.05%, 0.1%, and 0.5%, and compressive strength tests were performed, which showed an increase in the strength by 7.62%, 16.11%, and 26.82% at 28days of curing time. The TCLP and SPLP tests performed on the hybrid and cement-spent adsorbent mix showed all the leaching parameters were well within the permissible limits. This development shows the potential for the use of spent adsorbent in a circular economy model.

Exploration of novel high-temperature heavy metals adsorbent for sludge incineration process: Experiments and theoretical calculations

Adsorption is an effective and environment-friendly method to control the pollution of volatile and semi-volatile heavy metals (HMs) produced during municipal sludge incineration. In this study, the effect of a novel high-temperature adsorbent (attapulgite) on the migration and transformation mechanisms of HMs (Cr, Cu, Zn, Ni, and Pb) was investigated and compared with the conventional adsorbent (kaolin). The results of experiments and characterization showed attapulgite possessed improved adsorption effects than kaolin due to the smaller crystal distortion and more active sites reserved at 850 ℃. Furthermore, it was found that volatile HMs (Pb, and Zn) tend to be retained in the fly ash, while low-volatile HMs were adsorbed in the bottom slag by Si-Al-based absorbents. Meanwhile, the analytical results of BCR and TCLP tests showed that the proportion of unstable fraction of HMs in the adsorption products of attapulgite was much lower than that of raw dry sludge, and exhibited better leaching stability than kaolin. Theoretical calculations revealed that the adsorption of typical heavy metal forms at high temperatures by attapulgite exhibited a tight chemical adsorption, furthermore, the heavy metal oxides were more susceptible to removal by attapulgite (1 1 0) surface than the corresponding heavy metal chlorides. This work demonstrated the effectiveness of attapulgite in controlling heavy metals in furnaces and provided a new perspective on the development of this field.

Indirect bioleaching recovery of valuable metals from electroplating sludge and optimization of various parameters using response surface methodology (RSM)

Electroplating sludge contains amounts of valuable/toxic metals as a typical hazardous solid waste, but existing technology is hard to simultaneously gain the high recovery of valuable metals and its convert into general solid waste. In this study, indirect bioleaching process was optimized by using RSM for high recovery of four valuable metals (Ni, Cu, Zn and Cr) from electroplating sludge and its shift into general waste. The results showed that the maximum leaching rate respectively was 100% for Ni, 96.5% for Cu, 100% for Zn and 76.1% for Cr at the optimal conditions. In particular, bioleaching saw a much better performance than H2SO4 leaching in removal of highly toxic Cr (76.1% vs. 30.2%). The extraction efficiency of Cr by H2SO4 leaching sharply rose to 72.6% in the presence of 9.0 g/L Fe3+, suggesting that Fe3+ played an important role in the bioleaching of Cr. Based on bioleaching dynamics analysis, it was speculated that Fe3+ passes through the solid shell and enter inside the sludge to attack Cr assisting by extracellular polymeric substances (EPS), leading to high extraction and low residue of Cr. Meanwhile, due to high-efficient release and removal of valuable/toxic metals by bioleaching, the bioleached residues successfully degraded into general based on TCLP test and can be reused as construction material safely.

Clinkerisation of copper tailings to replace Portland cement in concrete construction

In this study, copper mine tailings were used as a replacement for Portland cement in concrete construction using sintering process. The applicability of the concrete samples was evaluated through TG, DTA, SEM, FTIR, XRD, and TCLP. The 28-day compressive strength of the concrete sample made of cement-substituted copper tailings was 42 MPa, which was 9% lower than that of the control sample. It was well supported using t-test with the p-value < 0.05. The TG and DTA tests results indicated that despite the presence of different compounds in the cement samples, the peaks of these tests were almost the same. The TCLP test results showed that the amount of studied heavy metals leaching in all concrete samples was lower than the standard limit (p-values less than 0.05). According to XRD and FTIR results, cement hydration process was well performed, and tricalcium silicate (alite) and dicalcium silicate (belite) phases were formed in the manufactured cement samples. In general, cement clinkers produced using Sungun copper mine tailings could be considered as a substitute for Portland cement in concrete construction.

Iron nanoparticles to recover a co-contaminated soil with Cr and PCBs

Little attention has been given to the development of remediation strategies for soils polluted with mixture of pollution (metal(loid)s and organic compounds). The present study evaluates the effectiveness of different types of commercial iron nanoparticles (nanoscale zero valent iron (nZVI), bimetallic nZVI-Pd, and nano-magnetite (nFe3O4)), for the remediation of an industrial soil co-contaminated with Cr and PCBs. Soil samples were mixed with nZVI, nZVI-Pd, or nFe3O4 at doses selected according to their reactivity with PCBs, homogenized, saturated with water and incubated at controlled conditions for 15, 45 and 70 days. For each sampling time, PCBs and chromium were analyzed in aqueous and soil fractions. Cr(VI) and Cr leachability (TCLP test) were determined in the soil samples. The treatment with the three types of iron nanoparticles showed significant reduction in Cr concentration in aqueous extracts at the three sampling times (> 98%), compared to the control samples. The leachability of Cr in treated soil samples also decreased and was stable throughout the experiment. Results suggested that nZVI and nZVI-Pd immobilized Cr through adsorption of Cr(VI) on the shell and reduction to Cr(III). The mechanism of interaction of nFe3O4 and Cr(VI) included adsorption and reduction although its reducing character was lower than those of ZVI nanoparticles. PCBs significantly decreased in soil samples (up to 68%), after 15 days of treatment with the three types of nanoparticles. However, nFe3O4 evidenced reversible adsorption of PCBs after 45 days. In general, nZVI-Pd reduced PCB concentration in soil faster than nZVI. Control soils showed a similar reduction in PCBs concentration as those obtained with nZVI and nZVI-Pd after a longer time (45 days). This is likely due to natural bioremediation, although it was not effective for Cr remediation. Results suggest that the addition of nZVI or nZVI-Pd and pseudo-anaerobic conditions could be used for the recovery of soil co-contaminated with Cr and PCBs.

Solidification/stabilization of Pb (II) and Cu (II) containing wastewater in cement matrix

This study reported solidification/stabilization of lead and copper-laden fly ash (adsorbent) utilizing cement as binder for their ultimate disposal. The Pb (II) and Cu (II) loaded fly ash was successfully immobilized within the cement matrix without presence of any chemical agents. A retardation of 80-100 minutes in the setting time of cement paste was noticed on the addition of metal-laden fly ash attributed to the presence of metal ions. However, a gradual decrease in mechanical strength of the mortars was observed with higher amounts of Pb (II) and Cu (II)-loaded fly ash in the mix composition. This gradual decrease is ascribed to the breakdown of calcium silicate hydrate (CSH) gel network in the presence of metal crystallites, as confirmed by scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) analyses. TG-DTG studies also reveal a decrease in CSH (%) from 4.77% (for fly ash cement mortar) to 4.14% and 3.86% for Pb (II) and Cu (II)-loaded fly ash mortars, respectively. X-ray diffraction (XRD) analysis of metal-laden fly ash cement mortars substantiate the immobilization of Pb (II) and Cu (II) metal ions in the cement matrix as peaks for Ca[Pb(OH)3]2 and Ca[CuH2O5Si] are visible in their patterns, respectively. TCLP tests conducted on 56 day cured metal-laden fly ash mortars show leachate concentration not exceeding the discharge standards. Overall, these results indicate that this integrated adsorption- solidification/stabilization process is efficient for safe disposal and utilization of heavy metal-laden fly ash for building and construction related work as a secondary material.

Interaction mechanism between arsenate and fayalite-type copper slag at high temperatures

The interaction mechanism between sodium arsenate and fayalite-type copper slag at 1200 °C was investigated through XRD, XPS, HRTEM, TCLP and other technical means and methods. The results indicated that the proportions of sodium arsenate in the slag and flue gas phases were approximately 30% and 70%, respectively. The addition of sodium arsenate depolymerized the fayalite structure and changed it from a crystalline state to an amorphous state. The fayalite structural changes indicated that the [AsO4] tetrahedron in sodium arsenate combined with the [SiO4] tetrahedron and [FeO4] tetrahedron through bridging oxygen to form a silicate glass structure. The TCLP test results of the samples before and after the high temperature reaction of fayalite and sodium arsenate showed that after high temperature reaction, fayalite could effectively reduce the leaching toxicity of sodium arsenate, reducing the leaching concentration of arsenic from 3025.52 to 12.8 mg /L before and after reaction, respectively.

A novel method for in situ stabilization of calcium arsenic residues via yukonite formation

Stabilizing the hazardous calcium arsenic residues (CAR) and monitoring the subsequent fate of arsenic (As) are critical to reduce its risk to the environment. In this work, a novel in situ method has been proposed to stabilize CAR by adding FeIII solution and subsequent formation of the secondary mineral (yukonite). The experiments were conducted at pH 6–9 with different Fe/As molar ratios (0.28–0.66) and the solid phases were characterized by using X-ray diffraction and scanning/transmission electron microscopy. Results showed that the stability of the CAR was significantly increased after the addition of FeIII solution, indicating good fixation effectiveness. The dissolved As concentration in the treated CAR samples continuously decreased to <5 mg/L after 490 days of treatment at Fe/As molar ratio ≥ 0.54 and pH ≥ 8, with the leached As concentration lower than 5 mg/L (US EPA standard) for most of the treated CAR in the TCLP and HVM tests. The formation of yukonite under different experimental conditions is closely related to the enhanced stability of the treated CAR. This work provides a novel in situ method to treat CAR which might have potential for future industrial applications.

Pengaruh Tekanan Blower pada Proses Pembakaran Sampah Medis Menggunakan Insinerator Statis terhadap Kualitas Abu

Medical waste generated from the activities of hospitals or other health facilities is very dangerous and can cause health problems for humans. One way of processing medical waste is by using an incinerator. This study aims to determine the effect of blower pressure on the medical waste incineration process on the levels of Cadmium (Cd), Chromium VI (Cr⁺⁶), and Lead (Pb) in the ash residue based on the TCLP test. The method applied is to weigh 300 kg of medical waste and then burn it in an incinerator with a blower pressure variation of 10 and 30 mbar at an optimal temperature of 1,200 °C. The results showed that the best TCLP test with a blower pressure of 10 mbar was Cd of 0.411 mg/L in experiment 2, Cr⁺⁶ of 0.143 mg/L in experiment 2, and Pb of 59.4 mg/L in experiment 3. Meanwhile, the results of the best TCLP test in Experiment 3 with a blower pressure of 30 mbar are Cd of 0.34 mg/L, Cr⁺⁶ of 0.098 mg/L, and Pb of 42.2 mg/L. The results showed that the levels of Cd and Cr+6 had met the environmental quality standards, while the Pb levels had not met the required environmental quality standards.

Utilization of copper mine tailings as a partial substitute for cement in concrete construction

Mine tailings generated during mineral processing activities are one of the major global environmental problems. In addition to accumulating in the environment and disrupting the environmental aesthetics, these tailings cause heavy metal pollution in the surrounding areas. In this research, Sungun copper mine tailings from Iran were used as a partial substitute for cement in concrete construction. Slump, compressive strength, chloride penetration resistance, and TCLP tests were performed on the prepared concrete samples. The results showed that the compressive strength of the concrete samples increased after 90 days of construction. Although the 90-day compressive strength of the control sample increased 4-fold compared to the age of 28 days, the samples made with 10–50% and 60–70% mine tailings as a cement substitute had a 5-fold and 7-fold increase in their compressive strength, respectively. According to the results, it could be concluded that cement hydration process and C-S-H crystals growth were more in the samples containing 10 to 70% mine tailings replacing cement compared to the control sample. Resistance to chloride ion penetration increased at the age of 28 days in the samples containing 10 to 40% Sungun copper mine tailings as a cement replacement, but decreased in the samples containing 50 to 70% mine tailings. However, after 90 days, from the perspective of the replacement of cement by tailings, resistance to chloride ion penetration was higher in the concrete samples compared to the control. Leaching of heavy metals (lead, zinc, copper, nickel, cobalt, chromium, cadmium, arsenic) in all the concrete samples was lower than the EPA standard allowable limit. Comparing the results of SEM and EDX images, it was found that after 90 days, the control sample had more ettringite than the sample made with 70% mine tailings replacing cement. Therefore, the concrete sample made with 70% cement-placing mine tailings was found to be more resistant to cracking over time.

Study of the operative conditions and the optimum amount of municipal incinerator bottom ash for the obtainment of ceramic floor tiles.

The idea of reusing municipal incinerator bottom ash (MIBA), the residue from incinerating municipal solid wastes, fits nicely in a circular economy scheme, which leads to an avoided impact of landfill disposal, and at the same time reduces the demand of natural resources. Past studies have attempted to add 20 to 60% MIBA for ceramic production, and resulted in some inspiring success. Focused on delivering quality interior and exterior floor tiles meeting industrial standards, this study investigated the operative conditions and the optimum amount of MIBA in the mix. In this study, only the kaolinite clay and MIBA were used. Before making specimens, raw materials of clay and MIBA underwent SEM, EDS, and TCLP tests to determine their chemical contents. Six sets of specimens with different replacement levels of MIBA (0%, 5%, 10%, 15%, 20%, and 30%) were then prepared. These specimens were fired at 1000°C, 1050°C,1100°C, and 1150°C and the products underwent a series of mechanical tests to verify their performance. NMR (nuclear magnetic resonance spectroscopy) were also used to determining the organic compound structure after each specimens' crystallization. Research results showed that proper mix of MIBA up to 20% could result in quality tiles complying with specifications for interior and exterior flooring applications at certain kiln temperatures, while the specimens with 30% MIBA failed to meet either bending strength or size shrinkage requirement at all four kiln temperatures, and could not deliver a satisfactory result.

Effect of using portland cement and tras soil to stabilize and solidify mercury-contaminated tailings in small-scale gold mining

Small scale gold mining in Kulon progo district using mercury for binding gold. The total concentration of mercury in tailings has 383.21 mg/kg. Stabilization/solidification is one of the remediation technologies to reduce waste pollution. This research aims to know the optimum composition in the S/S process. The first stage uses a composition between Portland cement: tras soil. the ratio are 100: 0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60., 30:70, 20:80, and 10:90. In the second stage, the tailings sample is added to the optimum from the first stage, with the composition of the binder: tailings. the ratio are 50:50, 40:60, 30:70, 20:80, and 10:90. The TCLP is applied according to the US EPA 1311 method. The first test results in the optimum composition of Portland cement: tras soil (10:90), the compressive strength test value of 96 kg/cm2. The compressive test result met the quality standards of The Head of Environmental Impact Control Agency (BAPEDAL) Decree KEP-03/BAPEDAL/09/1995 for the management of contaminated soil at 1 kg/cm2. The second test of binding: tailings (50:50) was 39.2 kg/cm2 with no detectable mercury concentration. TCLP test results meet the S/S product quality based on Government Regulation 101 of 2014 of 0.05 mg/L.

The Stabilization of Waste Funnel Glass of CRT by SiO2 Film Coating Technique

The funnel glass of the CRT monitor contains about 22–28% of lead oxide, of which lead is a highly toxic species and hazardous to the environment. This study proposes a process to form a protective layer of SiO2 film coating on the funnel glass to reduce the hazardous effect of lead leaching to the environment. The film coating benefits from the advantages of the sol–gel method. There are two key procedures of the stabilization technique, including the alkaline treatment and the formation of SiO2 coating from TEOS. The results show that the funnel glass powder treated with 10 M NaOH can produce a mushy layer on the surface. The mushy layer, which comprises OH− and water, can promote the formation of the SiO2 film layer on the surface of funnel glass powder. The conditions of the SiO2 film coating proposed in this study are: alkaline treatment by 10 M NaOH, the addition ratio of TEOS and funnel glass powder 2: 1, reaction temperature 40 °C, and reaction time 1.3 h. The EDS and ESCA results show that the Pb peak intensity on the surface of funnel glass decreases with the film coating. In the TCLP test, the leaching amount for Pb of the SiO2 film coated funnel glass powders is 0.7 mg/L, which is far lower than the standard in Taiwan EPA. Based on the experimental results, the formation mechanism of the SiO2 film layer on the surface of waste funnel glass powder is proposed. This study demonstrates that the SiO2 film coating is a potentially effective method to solve the problem of the waste funnel glass.

Highly effective remediation of high-arsenic wastewater using red mud through formation of AlAsO4@silicate precipitate

High-arsenic wastewater derived from the metallurgical industry of nonferrous minerals is one of the most dangerous arsenic (As) sources that usually follow the emission of massive hazardous arsenic-bearing wastes. Considering the properties of red mud (RM), we propose an alternative and environmentally friendly method for the efficient remediation of high-arsenic wastewater using RM through formation of AlAsO4@silicate precipitate, aiming at ''zero-emission of hazardous solid waste''. The results show nearly 100% of arsenic could be stepwisely removed from high-arsenic wastewater and reduce the arsenic concentration from 6100 mg/L to 40 μg/L using RM at room temperature. The highest arsenic removal capacity of RM reaches 101.5 mg/g at a RM-to-wastewater ratio of 40 g/L due to the superior arsenic adsorption and the co-precipitation of arsenate and Al3+ to form insoluble aluminum arsenate. The silicate shell of arsenic-loaded RM created at an alkaline condition acts as an arsenic stabilizer, resulting in a leached arsenic concentration of 1.2 mg/L in TCLP tests. RM acts as a highly effective arsenic remover and stabilizer for the disposal of high-arsenic wastewater. It shows great potential for the remediation of wastewater containing heavy metals with varying concentrations to produce clean water available for industrial purpose.